# Evaluate integral of a series

I want to evaluate this integral, but it won't work. Does anyone knows why?

Remove["Global`*"]

dm = (M/(2 π a)) a ;

i[ϵ_] = 1/(a Sqrt[1 - 2 (ϵ) Cos[θ] + (ϵ)^2]);
i1[ϵ_] = Series[i[ϵ], {ϵ, 0, 1}];
invertdist[r_] = i1[a/r];

ϕ[r_] = -Integrate[G dm invertdist[r], {θ, 0, 2  π}]
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There are two errors in your code: functions are defined with := and Series requires a symbol as a variable. –  Hector Mar 21 at 23:38